1. Field of the Invention
This invention relates to the side wall and top rail construction of open top containers for moving, transporting or storing materials.
2. Summary of the Prior Art
Open top containers for moving or storing materials generally have a bottom, side walls and end walls. The container is basically open at the top but may have a removable covering or have a non-rigid closed top. Examples of such containers are truck trailers, rail cars or scrap gondolas and are illustrated in U.S. Pat. No. Des. 238,259 and U.S. Pat. No. 4,252,067.
The conventional configuration of the side wall of these containers is a bottom rail attached to a rectangular horizontal floor and supporting vertical studs or side posts which carry a top rail. Cover sheets of material are fastened to the bottom rail, vertical studs and top rail to form the container. The bottom rail and top rail are designed to carry the load of the material in the container and the vertical studs and cover sheets contain the load.
In both open top and closed top containers the bottom rail is in tension. In open top containers, however, the top rail is in compression and must, therefore, be designed as a column also to carry the load within the container. As loads are increased, the compressive force is increased tending to buckle or bow the top rails outwardly or inwardly which may require the top rail size to be increased or may require the use of cross ties or trusses between the side walls. Such cross ties may be undesirable for freely loading and unloading the container and are subject to damage or removal by the container user. Thus, conventional container designs have relied on the top rail to carry the downward forces of the load as a beam and on cross ties to offset the compressive buckling of the top rail.